This disclosure relates to systems and methods of fitting hearing devices and more particularly to systems and methods of fitting hearing devices wherein measurements of the output of the hearing device are taken within the ear of the intended wearer of the hearing device.
In regards to the human auditory system, hearing aid devices (“hearing instruments”) are often used to compensate for hearing loss. The primary function of hearing instruments is to amplify the incoming signal in a manner appropriate to make the signal audible to the user. The amount of signal amplification may differ at various frequencies, normally audible to the human ear, based upon the degree of hearing loss at each frequency. Another important function of a hearing instrument is to limit the amplification of the incoming sound to a level that is not intolerable or uncomfortable to the user of the instrument.
Improving the audibility of human speech is the most important function of a hearing instrument. The hearing instrument's parameters affecting the amount of amplification and the limits of amplification are often adjusted to emphasize the speech signals that contribute most to the comprehension of human speech. Various frequency bands that are known to contain more useful speech information are emphasized or amplified more than other frequency bands containing less speech information.
A majority of hearing instruments currently fit to the human ear are both digital and programmable. These instruments have a multitude of parameters that are adjustable. These parameters are adjusted utilizing a computer or other hardware device, software dedicated to a particular manufacturer's hearing aid device, hardware that allows communication between the computer and the hearing aid device (such as HIPRO or NOAH LINK made by G. N. Otometrics), and a cable that connects the hardware to the hearing instrument. Adjusting these parameters to best benefit the user may be done by the dispenser of the device. The dispenser uses manufacturer provided guidelines, “first fit” or “best fit” protocols, fitting help guides, and in ear measurements, as well as their professional judgment, and subjective comments from the user, or any combination of the these tools to adjust the hearing instrument in an attempt to improve the audibility and comfort of speech signals as determined by the hearing loss of the user.
Hearing instruments have been designed based on the “average ear,” and do not take into account the structural differences among individual ears. Therefore, if a hearing instrument is used on an ear that differs structurally from the average ear, the hearing instrument could produce an insertion response that is substantially different from what one would expect based on average ear data. In addition, the measured insertion response may not match the target response. The many factors that contribute to actual response curves differing from prescriptive target curves include pinna effects, microphone placement, unusual external ears (concha, shape and size), and/or eardrums, abnormal middle-ear compliance (normal, flaccid, stiff), ear canal volume (length/diameter/shape), hearing instrument shell/earmold material (hard, soft), insertion depth, vent diameter and length, and resonant frequency of the user's ear canals.
Prescriptive procedures to determine the proper amount of gain, or sound pressure level (“SPL”) for hearing aids have been used as far back as 1960. The amount of gain adjustments suggested by the manufacturer's software to optimize the audibility and comfort of the incoming signal for the user of the hearing instrument is based on “average ear” canal and pinna resonance values. Analyzing tools have been developed to provide the dispenser with better information about the amount of frequency-specific amplification a hearing aid is providing to a specific user. These analyzing tools utilize a probe tube that is inserted into a hearing instrument user's ear canal between the hearing instrument and the patient's ear drum to measure the amount of hearing instrument output in an effort to provide the dispenser some degree of “real” ear instead of “average” ear information. Some of these analyzing tools produce simple or complex tones at various frequencies as input to the hearing aid device, which is then measured as output in the ear canal.
More recently, analyzing tools have been developed that utilize recorded or live speech as the input signal, such as the MedRx Avant™ REM Speech System. These devices provide the dispenser a better understanding of the audibility and comfort of important amplified speech signals.
The dispenser of a hearing instrument currently can use information derived from speech mapping analyzing tools and the various programmable parameters of the hearing aid device to manually adjust the device. These manual adjustments are undertaken in an attempt to provide the user of the device with improved speech audibility and comfort. These manual adjustments require professional knowledge and an understanding of the correct manual manipulations required in each hearing aid manufacturer's software. Because the adjustments are made manually, they are time consuming and therefore can contribute to the cost of a hearing aid device and possibly decrease the amount of time the dispenser has available to counsel the hearing instrument user about the care and use of the instrument. If the dispenser lacks sufficient experience, the adjustments may not be completed properly. As a result, the hearing instrument user might not receive the full benefit from the use of the device and/or may refuse to wear the instrument.
Thus, hearing instrument manufacturers, sellers and users would appreciate a system and method that facilitate automatically fitting hearing instruments to a user that senses the in ear response of the hearing instrument to speech stimuli and adjusts controllable parameters of hearing instrument.